As we all know, a firm handshake is important in making a good first impression. It's a sure sign of physical strength and, rightly or wrongly, we use it make all manner of judgements about character, personality ...

With the socio-economic developments of the last decades, new emerging compounds have been produced, released and discharged through different point and diffuse sources in European rivers, lakes, and marine-coastal and transitional ...

Submarine groundwater discharge (SGD) consists of a mixture of continental freshwater and seawater, which recirculates through the coastal aquifer. In addition to its importance in the water cycle, as a potentially ...

The malaria parasite Plasmodium falciparum produces chemical compounds called terpenes that give off odors that attract mosquitoes, according to new research. The study, published this week in mBio, the online op ...

In the current era of antibiotic-resistant bacteria, treatment of unwanted microbial growth presents a difficult challenge for microbiologists and clinicians. The problem is further complicated when these ...

Scientists at the Paul Scherrer Institute and ETH Zurich (Switzerland) have created 3D images of tiny objects showing details down to 25 nanometres. In addition to the shape, the scientists determined how ...

The development of reliable, convenient and cost-effective methods for drug analysis is crucial in the control and the fight against drug abuse. Hong Kong Polytechnic University (PolyU) has developed a new ...

Many chemical compounds exist as an image and a mirror image: they differ in their spatial orientation, like the left and right hand. The properties of these so-called chiral molecules are also often quite different – synthesising ...

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions and that have a unique and defined chemical structure. Chemical compounds consist of a fixed ratio of atoms that are held together in a defined spatial arrangement by chemical bonds. Chemical compounds can be compound molecules held together by covalent bonds, salts held together by ionic bonds, metallic compounds held together by metallic bonds, or complexes held together by coordinate covalent bonds. Substances such as pure chemical elements and elemental molecules consisting of multiple atoms of a single element (such as H2, S8, etc.) are not considered chemical compounds.

Elements form compounds to become more stable. They become stable when they have the maximum number of possible electrons in their outermost energy level, which is normally two or eight valence electrons. This is the reason that noble gases do not frequently react: they already possess eight valence electrons (the exception being helium, which requires only two valence electrons to achieve stability).